1. Field of the Invention
The present invention pertains to a sand control screen and installation method particularly adapted for open-hole and deviated or generally horizontally-extending wellbores.
2. Background
The use of so-called gravel pack or sand control screens is common practice in oil well completions. The installation of these screens in many applications is a delicate and troublesome exercise because of the tendency for the screen to become prematurely plugged with solids present in the well fluids and, in the case of so-called open-hole completions, the potential for collapse of the wellbore.
The problems associated with sand control screen installations are aggravated with the recent trend to drilling deviated and generally horizontal wells. These wells, in particular, are often completed without the installation of a casing or other formation support structure to improve well production and reduce cost of the well and due to the problems associated with installation of such structures. Conventional practice in drilling generally horizontal or deviated wells involves drilling the well to the desired length or "depth" followed by removal of the drillstring and the running in of a so-called completion string. During the removal and reinstallation of these pipe strings, there is a risk that the formation may collapse into the wellbore and reliance is usually placed on hydraulic pressure and the accumulation of so-called mud cake on the wellbore walls to prevent the "hole" from collapsing. Accordingly, there is significant risk of the wellbore collapsing, thereby requiring redrilling or abandonment of the well.
One solution to the above-mentioned problem is to drill the well with the sand control screen in place as part of the lower end of the drillstring. However, this type of operation requires leaving the drillbit in the wellbore or providing a drillstring with a retrievable bit or bit and motor assembly such as that described in U.S. patent application Ser. No. 07/744,859, filed Aug. 14, 1991 by Richard E. Leturno and assigned to the assignee of the present invention. The placement of a sand control screen in the drillstring and making the lower end of the drillstring a permanent part of the well completion assembly is attractive. However, the above-mentioned arrangement still presents certain problems in avoiding premature plugging of the sand control screen with solids and completing the production string assembly. The present invention overcomes some of these problems as will be further described herein.